The molecular basis for the neurological problems associated with HIV infection is not well, but is likely to involve a combination of virally- encoded proteins, their receptors, and secreted proteins made by resident of infiltrating cells in the central nervous system. The Protein Chemistry Core (PCC) will provide support for the chemical synthesis, expression and mass spectroscopic analysis of these proteins and their peptide fragments. Synthetic access to small proteins such as chemokines, cytokines, smaller HIV encoded proteins such as Tat and individual domains from larger proteins will enable neuroAIDS researchers to site- specifically incorporate unnatural groups such as fluorophores, crosslinking agents and affinity tags to protein. These proteins will be assembled from the smaller peptide fragments using recently developed chemical ligation techniques. In addition, the PCC will provide support for the synthesis of peptides for the generation of antibodies, peptide- based enzyme inhibitors and peptidomimetics. The PCC will also provide support for protein expression in multiple expression systems, including bacterial, mammalian, and insect cell culture and state-of-the-art procedures for their purification. Finally, training and hands-on access to electrospray and MALDI mass spectrometry will facilitate neuroAIDS researchers in mapping of post-translational modifications, in identification of unknown proteins, and in obtaining high resolution mass data to analyze the purity and composition of expressed or purified proteins. In this manner, the PCC will greatly enhance the ability to neuroAIDS researchers to obtain, analyze and manipulate proteins in their research projects.